(1) Field of the Invention
This invention relates to a bearing material which is made by sintering the powder of a Cu-Pb base alloy or its constituent metal powders on a backing steel sheet. Kelmet is well known to those skilled in the art as a Cu-Pb base sintered bearing alloy having excellent seizure resistance, load resistance and wear resistance. In the present invention, the properties of this Cu-Pb base sintered alloy are much improved, and the sliding characteristics relative to a contact material having a rough surface are especially improved in this novel sliding material.
(2) Description of the Prior Art
As the sintered alloys for use in making bearing materials, there are known in the prior art several alloys containing copper, lead, antimony and/or tin. Among them, Kelmet is a bearing alloy consisting mainly of copper and lead, and it has excellent seizure resistance, load resistance and wear resistance as mentioned above. It is, therefore, regarded as suitable for high speed, heavy duty purposes and is widely employed in bearings for the engines of airplanes, automobiles and the like. The above properties of the bearing material, however, largely depend upon the contact pressure, sliding speed and other operating conditions existing between the bearing surface and the contact material to be supported, and upon the hardness and other properties of the contact material itself.
For example, in spheroidal graphite cast iron and ordinary cast iron having rough surfaces, spherical or flaky graphite particles fall off from the sliding surface so that the sliding surface becomes rough. The pointed edges of this rough surface formed by the falling-off of graphite particles scratch the bearing material. Therefore, the lead particles embedded in the bearing material become liable to fall off, resulting in abnormal wearing of the bearing material. For the above reason, when the bearing material of this kind in the conventional art is brought into contact with a rough surface, the seizure resistance becomes worse in a short time, therefore, such the material is quite disadvantageous in practical uses.